A plurality of such rotors for electrical machines, having metal sheets laminations disposed on them, which are generally combined into bundles, is known from the state of the art. They are used, for example, in asynchronous machines and in permanently excited synchronous machines. All electrical machines are greatly heated during operation, because of the electromagnetic activity in the rotor and as the result of the heat transfer to other weight-optimized supporting components that takes place. Different concepts for fluid cooling, to limit heating, are known from the state of the art. In this regard, the known cooling systems are accompanied by a specific rotor design, which makes use of special coolant guide structures, for example. Other concepts also require a great number of additional components, which influence not only the design of the rotor but also that of the machine and the interface components.
Different solutions for guidance and distribution of the cooling medium to the heat transfer surface are also known, most of which have a complete line for the coolant, in channels or bores, laid out over the entire axial and radial path distance, as a compulsory guide. Such compulsory guides bring about a great pressure loss, caused by the flow resistance, so that coolant pumps become necessary, particularly if a flow direction opposite to centrifugal force is included. Furthermore, implementation of these concepts is particularly complicated because of the great number of bores, particularly axial hole bores.
Certain types of cooling, as they are shown, for example, in DE 11 2010 004 773, integrate additional components into the rotor, but these require additional mounting and sealing. Furthermore, electrical machines having hollow shafts are also known, for example from CH 337267, in which machines the entire cavity of the rotor must be filled with fluid in order to achieve sufficient interaction of the cooling fluid with the rotor cylinder barrel, and good heat transfer. However, it has been shown that it is not possible to conduct a sufficient amount of heat away in this manner.
Ultimately, all known cooling devices have one of the following disadvantages: Either overly small cross-sections of the lines provided for the coolant are selected, in order to reduce the volume requirement. However, such small passage bores hardly reduce the weight of the rotor shaft to be cooled. Furthermore, the coolant can be conducted to the components to be cooled, particularly to the sheet-metal packet, which particularly heats up, only to a slight extent, because the surfaces are small, in any case. The coolant often wets only small surface areas of the heated surface, and no large-area distribution over the entire circumference comes about.
On the other hand, not only a large surface for heat transfer but also a particularly easy method of construction can be implemented with large line cross-sections and cavities in the rotor shaft. However, in this case it is disadvantageous that the hollow cylinder must be filled almost completely with coolant during operation, which increases the coolant requirement and in turn leads to an increase in the moving mass, something that was specifically supposed to be avoided by the light-construction design.